The present invention relates generally to knives of the folding kind and, more particularly, knives that spring open automatically.
Knives generally and particularly folding knives are well known and have been in use in the public for ages. All these prior art knives include common elements. Among these elements are an elongated handle that typically is split into two sides separated from each other to form a spacing. A blade having a working end and a pivot end located in the tang is pivotally disposed at one end of the handle so as to fill the spacing in the handle when in the closed or folded position and when in the open or working position, the knife blade pivots about the end of the handle and extends outwardly. For an automatic or spring opening folding knife, some form of retaining means is used to retain the blade of the knife recessed in the spacing unless and until released by a mechanism that allows the blade to pivot and spring outwardly to attain a working position.
Numerous mechanisms are known in the art for automatically pivoting the knife blade into working position from its recessed or closed position and essentially all use some form of spring means to achieve this pivoting action. Different forms of such springs have been devised for achieving the desired pivoting action.
Regarding the retaining means that operates as a trigger to release the blade from its closed or recessed position to attain its open or working position, there are many different triggering mechanisms. For safety reasons it is particularly desirable to retain the blade in a closed recessed position that essentially is locked in such position unless and until released by the retaining mechanism. Similarly, when the knife blade is in the open or working position it is completely unacceptable for the blade to prematurely close. Rather the blade when in the open or working position must be locked in that position until it is desired to pivot the blade to its closed or recessed position.
A typical folding knife of the prior art is disclosed in Brooker, U.S. Pat. No. 4,897,922. This patent discloses a folding knife, which though not an automatically opening knife, does disclose a knife blade and a handle having a slot for storage of the blade in a closed position. This patented folding knife also provides for the blade attaining a working position wherein the blade may be rotated 180xc2x0 out of the slot in the handle. A lock member is rigidly attached to a threaded shaft that is threaded into a square bolt, welded or otherwise permanently affixed to the knife handle. The lock member may be manually rotated about the axis of the threaded shaft to move the entire lock member upwardly relative to the handle and blade combination in order to align a notch positioned in the lock member over the top of an abutment portion at the end of the blade. The blade then is free to be pivoted from an open position to a closed position.
Then when the lock member is rotated to move downwardly along its vertical axis, the notch moves to a position remote from the abutment portion of the blade, the planar bottom portion of the lock member holds the blade in a locked position.
This patented construction, while having some usefulness, cannot lock the blade closed when in the folded position due to the eccentric pivot axis of the blade in relationship to the lock member. Accordingly, such a knife does not have the desired safety features wherein the blade would be locked in place whether in an open or a closed position.
The patent to Barrett, U.S. Pat. No. 4,167,811, discloses a rotatable locking sleeve with a longitudinal slot designed to register with a different slot to free the blade. The axis of the locking sleeve as disclosed in this patent is aligned with the axis of the handle and the blade rather than being transverse.
The patent to Sakurai, U.S. Pat. No. 5,915,792, discloses a ratchet wheel with a pair of notches that operates with a locking lever and pawl.
Collins, U.S. Pat. No. 3,930,309, discloses a ring lock that rotates to align slots in the ring lock and handle to permit the blade to be open.
The present invention relates to a folding knife that opens automatically. The knife includes an elongated handle having opposing separate sides forming a spacing therebetween. An elongated blade having a working end and a tang at the opposite end is pivoted at a pivot axis to the handle at the tang end of the blade to permit the blade to pivot into an open or working position where the blade extends outwardly from the handle and alternately into a closed or folded position where the blade is recessed into the spacing. The blade is urged into an open position by a blade biasing means in the form of an axial spring surrounding the pivot axis and extending completely through the thickness of the blade. The axial spring is connected at its ends between the blade and the handle.
A locking element, in the form of a wheel, controls the movement of the blade into its open position by being rotatably positioned about an axis of rotation transverse to the pivot axis of the blade while being located and held within the handle for rotary movement only. A cutout is positioned on the locking element to cooperate with the tang to permit passage of the tang therethrough during pivotal movement of the blade. The locking element is further rotatably actuatable selectively to both an unlocked position wherein the cutout coincides with the tang to permit the passage of the tang and therefore the blade and also a second position where the locking element provides an abutting relationship with the tang for locking the blade from movement both when in an open position and when in a closed position.
This invention also includes a coil spring having a greater number of turns in the coil as the axial spring that forms the blade biasing means. This coil spring surrounds the pivot axis and extends completely through the thickness of the blade. A sleeve attached to the tang surrounds the pivot axis and has ridges extending beyond both sides of the blade. One end of the coil spring is held in a slot formed in one of the ridges while the other end of the coil spring is secured to the handle.